Electrodes from carbon powders are used widely in electroanalytical chemistry. There is an increasing interest in electrodes prepared from sulfides, carbides, silicides, nitrides, borides and oxides of transitional metals (J. L. Anderson, E. Bowden, P. Piceep. Anal. Chem., 1996, v.68, pp. 379R-444R). These refractories are produced as conductive powders with high chemical and electrochemical stability. The main difficulty in preparation of electrodes from such powders is the high specific electrical resistance of the initial powdery material (.rho..gtoreq.10.sup.6 .OMEGA..multidot.cm), high hardness (5-9 units on the scale, in which diamond hardness is 10 units) and high melting temperatures (2500-3000.degree. C.).
Two main kinds of such electrodes are widely used: paste and sintered electrodes. Carbon paste electrodes are produced from mixtures of a carbon powder with an inert liquid (paraffin oil, silicone etc.) which is an electrical insulator and which is insoluble in the electrolytes used. The drawbacks of carbon paste electrodes are their relatively low stability and reproducibility (E. Gun, M. Tsionsky, O. Lev. Anal. Chem., 1994, v.66, pp. 261-270).
Solid electrodes from carbon powder with different polymers (Teflon.COPYRGT., epoxy resin, polyacrylamide etc.) are known (L. Falat, Ch. Y. Cheng. Anal. Chem., 1982, v.54, pp. 2108-2111). Preparing such electrodes from low conductivity powders (for example, titanium nitride) is practically impossible because of the high resistance of the electrodes (R.gtoreq.10.sup.4 .OMEGA.). The attempt of sol-gel technology application for preparation of electrodes from low conductivity powder of V.sub.2 O.sub.5 was unsuccessful due to this reason. (V. Gleser, O. Lev. J. Amer. Soc., 1993, v.115, p.2533). Similar is the use of screen-printing paste (J. Rohm, W. Kunneka et. al. Anal. Chem., 1995, v.67, pp. 2304-2307) which has the same drawback--high electrical resistance of electrodes.
B. Filanovsky, L. Nadezina et. al. (Zav. Lab., 1988, v.54, N 2, pp.13-16) used high temperature dusting of powder on a corresponding matrix for titanium nitride powder. This method does not allow to eliminate the effect of the matrix on the measurement results. Besides, this technology is complicated and expensive.
The most effective method for preparation of electrodes from powders with high electrical resistance is high temperature treatment (sintering) of previously pressed powder tablets in an inert atmosphere. B. Hofman and H. Shell (Electrokhimiya, 1988, v. 24, pp.1199-1203 and 1264-1267) prepared electrodes from titanium carbides Ti.sub.x C.sub.y and titanium nitrides Ti.sub.x N.sub.y, where 0,7&lt;x&lt;1,5 and 0.7&lt;y&lt;1.5, at the temperature .about.2000.degree. in hydrogen atmosphere. This is a precursor of our invention. The drawback of the known method is the dependence of electrochemical properties of the electrodes produced on the preparation conditions (temperature, pressure and composition of atmosphere) which influence the stoichiometry and porosity of the product.
Evaluation of the novel electrodes in analytical methods is usually conducted by comparison with the most widely used glassy carbon electrodes (see, for example, J. W. Strojek, M. Grander, G. Swan. Anal. Chem., 1996, v.68, pp. 2031-2037).